2012

Spline-fit polylines are very different from the curves produced by the Fit
option. Fit constructs pairs of arcs that pass through every control point. Both
of these curves are different from true B-splines produced with the
SPLINE
(page 988) command.
If the original polyline included arc segments, they are straightened when the
spline's frame is formed. If the frame has width, the resulting spline tapers
smoothly from the width of the first vertex to the width of the last vertex. All
intermediate width information is ignored. Once spline-fit, the frame, if
displayed, is shown with zero width and CONTINUOUS linetype. Tangent
specifications on control point vertices have no effect on spline-fitting.
When a spline-fit curve is fit to a polyline, the spline-fit curve's frame is stored
so that it can be recalled by a subsequent decurving. You can turn a spline-fit
curve back into its frame polyline by using the PEDIT Decurve option. This
option works on fit curves in the same manner as it does on splines.
Most editing commands act the same when applied to spline-fit polylines or
fit curves.

MOVE (page 671), ERASE (page 406), COPY (page 228), MIRROR (page 647),
ROTATE (page 907), and SCALE (page 916) operate on both the spline curve
and its frame, whether the frame is visible or not.

EXTEND (page 410) changes the frame by adding a new vertex where the
initial or final line of the frame intersects the boundary geometry.

BREAK (page 155) and TRIM (page 1067) generate a polyline with only the fit
spline, which is consistent with fit curves, where the curve fitting is
permanent.
 EXPLODE (page 407) deletes the frame and generates lines and arcs to
approximate the spline-fit polyline.

OFFSET (page 715) generates a polyline with only the fit spline, which is
consistent with its behavior with fit curves.

DIVIDE (page 356), MEASURE (page 611), and the Object option of AREA
(page 83) and HATCH (page 471) see only the fit spline, not the frame.
 STRETCH (page 1004) refits the spline to the stretched frame after a spline
is stretched.
774 | Chapter 2 Commands